Method of manufacturing the oxide dispersion strengthened ferritic steel having excellent high-temperature creep strength with a coarse grain structure

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing ferritic oxide dispersion strengthened steel which has a coarsened and equiaxed grain structure effective in improving the high temperature creep strength of ferritic oxide dispersion strengthened steel.;SOLUTION: Powders of elements or powders of alloys are mixed with Y₂O₃ powder, and the resultant powder mixture is mechanically alloyed, solidified by hot extrusion and then subjected, as final heat treatment, to heating and holding to and at a temperature not lower than the Ac₃ transformation point and subsequent slow cooling heat treatment at a rate not higher than the critical rate for ferrite formation. In this way, the ferritic oxide dispersion strengthened steel which has a composition consisting of, by mass, 0.05 to 0.25% C, 8.0 to 12.0% Cr, 0.1 to 4.0% W, 0.1 to 1.0% Ti, 0.1 to 0.5% Y₂O₃ and the balance Fe with inevitable impurities and in which Y₂O₃ particles are dispersed can be manufactured. When manufacturing the steel, TiO₂ powder is used as element powder for a Ti component to be mixed in the mechanical alloying treatment to suppress the bonding between Ti and C and prevent the decrease in C concentration in a matrix.;COPYRIGHT: (C)2004,JPO